During the past half century, the fields of transplantation and immunology have met many of the same challenges and advanced together in both the basic and the clinical arenas. For example, observations regarding the fate of transplants in humans and experimental animals provided the foundation for the fields of immunogenetics and cellular immunology. At the same time, basic studies in immunology have given rise to modern immunosuppressive therapy and provided tools for analyzing transplant outcomes. The interdependence of transplantation and immunology has grown in recent years as knowledge concerning the molecular basis for transplant rejection has pointed to new, rational approaches to the development of immunomodulatory agents and tolerance. This rapid advance is exemplified by emerging efforts in the field of xenotransplantation, in which the identification of molecular hurdles has given rise to the genetic engineering of transplant donors. Still, as in many fields, the basic and clinical research in transplantation has not been integrated to an optimal extent. The goal of this conference is to consider in detail the molecular biology and cell physiology of immune responses which contribute to the rejection of transplants and to the induction of immunological tolerance. The conference will bring those engaged in clinical and experimental transplantation together with those involved in basic investigations to reconsider the current base of knowledge and identify future challenges and approaches.